PROBLEM TO BE SOLVED: To prevent lateral tear of a side seal part caused by a sheet bonding part.SOLUTION: A stretchable area adjacent to a central side in a width direction of a side seal part in an exterior body has a plurality of slender elastic stretchable members extending along the width direction that are arranged between two sheet layers 12S, 12H with intervals in a back and forth direction. The elastic stretchable member is a fixed-end part whose width direction both end parts are fixed to two sheet layers and is not fixed to the two sheet layers between the fixed-end parts. In an area between the fixed-end parts in the stretchable area, the two sheet layers are welded at a part between the elastic stretchable members adjacent in a back and forth direction via a sheet bonding part virtually succeeding in the width direction. In a first area 13A and a second area 13B evenly dividing the side seal part 13 into two in the width direction, a welding part 13s is provided in an intermittent and regular pattern. In an underpants type disposable diaper, peel strength of the first area is weaker than peel strength of the second area.SELECTED DRAWING: Figure 23【課題】シート接合部に起因するサイドシール部の横裂けを防止する。【解決手段】外装体における、サイドシール部の幅方向中央側に隣接する伸縮領域は、２枚のシート層１２Ｓ，１２Ｈの間に前後方向に間隔を空けて配置された、幅方向に沿って延びる複数本の細長状の弾性伸縮部材を有し、弾性伸縮部材は、その幅方向両端部が２枚のシート層に固定された固定端部とされ、これら固定端部の間では２枚のシート層に固定されておらず、伸縮領域における固定端部の間の領域では、２枚のシート層が、前後方向に隣接する弾性伸縮部材の間の部位で幅方向に実質的に連続するシート接合部を介して溶着され、サイドシール部１３を幅方向に二等分した第１領域１３Ａ及び第２領域１３Ｂのそれぞれに、溶着部１３ｓが縦方向に間欠的かつ規則的パターンで設けられ、第１領域の剥離強度が第２領域の剥離強度よりも低い、パンツタイプ使い捨ておむつである。【選択図】図２３
